(1) Field of the Invention
The present invention relates to an apparatus for periodically dispensing a fluid over an area by spraying. In particular, the present invention relates to an apparatus for electronically controlling the periodic spraying of a liquid in controlled amounts over a specified area. The present invention particularly relates to an electronic micro-dispensing apparatus for spraying pheromones in controlled amounts for a short duration in timed intervals to control insects in an outdoor setting such as an orchard.
(2) Description of the Related Art
The patent art has shown various types of automatic dispensing systems and apparatus. Illustrative are U.S. Pat. No. 3,627,205 to Healy; U.S. Pat. No. 4,272,019 to Halaby, Jr.; U.S. Pat. No. 4,671,435 to Stout et al and U.S. Pat. No. 5,074,468 to Yamamoto et al. In addition, U.S. Pat. No. 2,524,796 to Higgins; U.S. Pat. No. 3,667,673 to Knudsen and U.S. Pat. No. 3,926,369 to Pearce show spraying apparatuses which spray automatically in response to a specific environmental condition.
U.S. Pat. No. 4,671,435 to Stout et al describes a solenoid operated valve. The problem is that the nozzle and the valve are not joined together as in a fuel injector. The result is that there is less precision in the metering of the fluid to be sprayed.
In particular, U.S. Pat. No. 4,473,186 to Alperin describes a method and apparatus for spraying aerosols comprising small liquid or solid particles as fine mist over large distances on the order of 120 ft while using minimal amounts of energy. The method and apparatus utilize the property of the ejector normally employed for moments or thrust ignition for dispersement of the liquid and solid aerosols over large distances with large divergence angles. The apparatus and method cause the substance to be sprayed to mix with a high velocity jet, thus causing an acceleration of the substance in the desired direction utilizing the drag force for projection over large distances rather than for deceleration and small spray distances.
Further, U.S. Pat. No. 3,305,134 to Carmichael describes an automatic spray device which will automatically and periodically dispense a compressed fluid. The device is used in connection with a pressure pack or aerosol container. The device comprises regulator valve mechanics connected to the pressure pack for regulating the exit flow of the propellant contained in the pressure pack and a diaphragm type valve in a chamber. The diaphragm type valve controls the flow of the fluid. When the propellant from the pressure pack accumulates and provides a proper pressure on the diaphragm valve, the valve will open, thus spraying the fluid. The device can be constructed with a separate container for the propellant or the fluid and propellant can be combined in the same container.
U.S. Pat. No. 3,523,646 to Waldrum describes a liquid sprayer which discharges the liquid in a direction opposite the direction of movement of the nozzle. The movement and direction of flow causes the uniform formation of droplets, which reduces the problem of drift.
In the past, pheromones for disruption of insect chemical communication have been released from impregnated solids like rubber and plastic in sizes ranging from sprayed microcapsules to foot-long strips hung on trees, open-ended hollow fibers where evaporation rate is controlled by size of the openings, and hollow polyethylene tubes having their lumen filled with chemical and heat-sealed at the end. Release rate from these "ropes" or other such releasers having an undiluted chemical reservoir is most preferably constant until the reservoir is exhausted.
A disadvantage of the above-mentioned dispersers is that they are perpetually "on" once deployed and cannot retain their chemical during periods when, due to pest life cycle, there may be no need to dispense the chemical. Dispensing the chemical only when needed is something that is economically desirable. Within the past two years, applied entomologists have adapted automatic aerosol dispensers to surmount this problem of wasting precious volatile chemicals by dispensing them indiscriminately over time. Automatic aerosol dispensers are used to dispense or sometimes fumigants for insect pest control at timed intervals. At the intervals (e.g., 30 min. interval) a battery-powered motor turns gears attached to a lever that depresses the valve of an aerosol can, emitting a short pulse of can contents. Because many moth pests mate only at night, the automatic aerosol dispensers used for insect sex attractant release employ a photocell that precludes release in daylight. For this application, pheromone must be formulated with a propellant and packaged in a conventional spray can, which protects chemicals from exposure to the degradative factors of light and oxygen. The aerosol sprays onto a cloth pad from which is evaporates at a decreasing rate between pulses of spray.
Currently available are automatic aerosol dispensers which require a substantial amount of force (about 4 kg) to depress the aerosol can control valve. In addition, the mechanics and circuitry used to depress the aerosol control can valve on existing models are not maximally efficient and hence are more expensive than necessary. Furthermore, expensive and specialized equipment is required to charge or recharge an aerosol can. The currently available aerosol dispensers also have limited flexibility in control of their release of chemicals.
There remains the need for an electronically controlled micro-dispensing apparatus which allows for controlling the duration and amount of the spray as well as the time interval between spraying and which is economical to manufacture and operate.